A common problem that exists for those responsible for managing large buildings such as factories, warehouses and offices, is energy wastage. It is desirable to reduce energy consumption as much as possible while ensuring that normal activities may proceed with little or no disturbance. Efficient control of lighting is a common goal for building managers.
Various attempts have been made to control lighting based on the presence of personnel or activities in a given area. In the simplest instance, personnel manually turn on and off lighting in the area they are entering and leaving. This has the disadvantage that normal activity may be interrupted by this process and this may even pose a safety hazard, especially if the person in question is handling materials that may be hazardous but must set down and picked up in order to turn on and off the lights.
In a well known solution to control lighting in situations such as described above, a person may be required to activate a time-delayed switch which causes the lights to be turned on and then turn off automatically after a predetermined time, said time being sufficient for the person to carry out the required activity and leave the lighted area. This has the disadvantage that if the person requires more time than the pre-programmed ‘on’ time, they may be left without light, presenting a safety hazard.
Another common approach, as disclosed by Szuba in U.S. Pat. No. 5,220,250, is to activate lights based on detecting the presence of personnel using a sensor. The sensor may be one of a number of types, such as a microwave sensor, a passive infrared sensor or ultrasonic sensor, each usually activated by the movement of personnel in a particular area. The sensors may be attached to individual luminaires or may be separately placed to detect movement and activate individual luminaires or otherwise a plurality of luminaires representing zones of illumination, such as a section of a warehouse.
There are major drawbacks to the aforementioned detection approach. In the case of the first instance, wherein each luminaire is controlled by its own sensor, the problem is that, although it is very energy efficient, the area illuminated is too small for normal human activity and is therefore undesirable. In the second case, where a sensor activates a number of luminaires, it is necessary to wire the luminaires into zones which are activated by the sensor. The delineation of such zones is determined during initial installation and commissioning and may, after a period of time, not relate usefully to the changing needs for illumination as changes occur in the boundaries of activities required to be undertaken by personnel. For example, the relocation of an assembly line may result in it overlapping two lighting zones making it impossible to optimize the efficiency of the lighting system.
In more recent times, there has been an attempt to optimize lighting in buildings using computerized building management systems as taught by Huizenga (U.S. Pat. No. 7,623,042). Such systems are able to receive inputs from sensors placed in a building and perform logical operations to turn on and off facilities such as heating and lighting. In this case, the system suffers the disadvantage of the cost of wireless links required to provide the logical connectivity between luminaires, sensors and the control unit. For systems where the sensing information and power control are provided over wires, there is a considerable cost associated with the installation of said wiring. In all such cases the cost of the control units and separate sensors add further to the cost burden. A further disadvantage is that, as with other centralized systems, the luminaires are wired into zones during commissioning. Such zones are normally as large as possible as this minimizes the cost of wiring and the cost of interfaces. As a result the granularity of control of lighting is limited to the size of the zones which limits the extent to which energy usage may be optimized.
A very common drawback of automatic lighting control systems is that at the cessation of activity, and usually after a further delay period, the luminaires are turned off. This has a very distracting effect on personnel working nearby. Although the area that the person is working in may be well illuminated, sudden changes in peripheral illumination may cause distraction and negative safety or productivity effects. What is needed are improved apparatus, methods and systems for illuminating specified areas more efficiently and cost-effectively than those currently known.